Safety device for limiting the rotational speed of internal combustion engines

ABSTRACT

An electronically controlled diesel engine wherein the highpressure chamber of the fuel injection pump is connected with the low-pressure chamber by a passage controlled by an electromagnetic valve which opens or closes when the rotational speed of the engine reaches a maximum permissible value. The speed is detected by an electrical counter which effects opening of the valve if the latter is installed in a passage which conveys fuel from the high-pressure chamber, or closing of such valve if the latter is installed in a passage which supplies fuel to the high-pressure chamber, whenever the engine speed reaches the maximum permissible value. The electrical connection between the speed counter and the valve comprises an amplifier whose input circuit contains an inductance of the speed counter and a first safety fuse and whose output circuit contains a relay switch for the circuit of the winding in the valve and a second safety fuse. The circuit of the winding can be completed by an auxiliary switch in response to actuation of the starter for the engine.

May 9,1972

United States Patent Eheim [54] SAFETY DEVICE FOR LIMITING THE FOREIGNPATENTS OR APPLICATIONS ROTATIONAL SPEED OF INTERNAL COMBUSTION ENGINES[72]. Inventor:

996,032 6/l965 GreatBritain...................123/198DB PrimarvExaminer-Laurence M. Goodrid e Franz Stuttgart Germany Attornei-Michaels. Striker g Assignee: Robert Bosch GmbH, Stuttgart, Germany Filed: Mar.17, 1970 [57] ABSTRACT An electronically controlled diesel enginewherein the high- [21 1 Appl' pressure chamber of the fuel injectionpump is connected with the low-pressure chamber by a passage controlledby an elec- [30] Foreign Application P i i Data tromagnetic valve whichopens or closes when the rotational speed of the engine reaches amaximum permissible value. The speed is detected by an electricalcounter which effects Mar. l9, 1969 Germany...........,..........P l9 13808.0

opening of the valve if the latter is installed in a passage whichconveys fuel from the high-pressure chamber, or closing of [52] U.S.Cl.........................123/140 A, 123/102, 123/139 E [51]Int.Cl.......

Field of Search reaches the maximum permissible value. The electricalconnection between the speed counter and the valve comprises anReferences Cited amplifier whose input circuit contains an inductance ofthe speed counter and a first safety fuse and whose output circuitUNITED STATES PATENTS contains a relay switch for the circuit of thewinding in the valve and a second safety fuse. The circuit of thewinding can 3,356,082 12/1967.lukes.............,.......................123/102 be completed by anauxiliary switch in response to actuation e n me n e e h t r m r e n a tS e h t f O X mu 2 B0 1 3 2 Wm t e r. "6 Km we K.. 0 KS 35 66 99 ll 7548 54 92 98 33 3,326,l99 6/1967McMillen...........,.......,.......123/148E 9Claims,2DrawingFiguresPATENTEDMM 91972 SHIN 1 [IF 2 FIG. I.

- JNVt'A/TOR Fro/n2 EHE/M PATENTEDMY 91912 7 3.661.130

SIHH 2 OF 2 /N I/E N701? I Franz EHE/M h/ls ATTORNE Y SAFETY DEVICE FORLIMITING THE ROTATIONAL SPEED OF INTERNAL COMBUSTION ENGINES BACKGROUNDOF THE INVENTION The present invention relates to internal combustionengines in general, and more particularly to improvements in safetydevices which limit the rotational speed of internal combustion engines,especially of electronically controlled diesel engines. Still moreparticularly, the invention relates to improvements in safety devicesfor internal combustion engines with fuel injection.

It is well known that a diesel engine cannot be operated at speeds whichexceed a certain value. Such value is determined by the structuralcharacteristics of a particular engine. If the engine operates at amaximum permissible speed and its cylinders continue to receive fuel,the speed can increase beyond the permissible value but with theattendant danger of substantial damage. The likelihood of overspeedingis less pronounced in gasoline driven engines where the speed is limitedby flow resistance of fuel supplying passages.

At the present time, diesel engines are normally equipped withcentrifugal governors which control the flow of fuel to the fuelinjection pump. The rate of fuel flow is reduced whenever thecentrifugal governor detects a certain operating speed which should notbe exceeded. Such centrifugal governors are rather bulky and expensive.Also, they are not ideally suited for use in internal combustionengines, particularly diesel engines, whose operation is regulated by anelectronic control circuit.

SUMMARY OF THE INVENTION An object of the invention is to provide aninternal combustion engine, particularly an electronically controlleddiesel engine, with a novel and improved safety device which limits thespeed of the engine and is just as reliable as but more compact than aconventional centrifugal governor.

A further object of the invention is to provide a versatile safetydevice which can be used in many types of internal combustion engines.

An additional object of the invention is to provide a safety devicewhich is constructed and assembled in such a way that it can preventoverspeeding of the engine even if one or more ofits components happento be defective.

An ancillary object of the invention is to provide a safety device whichcan be combined with or incorporated into the fuel injection pump ofadiesel engine.

The invention is embodied in an internal combustion engine, particularlyin an electronically controlled diesel engine, which comprises a fuelinjection pump having a high-pressure fuel chamber, a low-pressure fuelchamber and a passage connecting the two chambers, a rotary memberarranged to rotate at a variable speed which is proportional to (and maybe identical with) the operating speed of the engine, electromagneticsafety valve means including a valve member installed in the fuelinjection pump and movable between open and closed positions in which itrespectively permits and prevents the flow of fuel though the passage,the valve member assuming one of its positions in response toenergization and the other position in response to deenergization of thevalve means, and electrical speed counter means operatively associatedwith the rotary member and arranged to effect a change in the conditionof energization of the valve means when the speed of the rotary memberreaches a predetermined maximum value.

The valve member is moved to closed position in response todeenergization of the valve means if it is installed in a passage whichsupplies fuel from the low-pressure chamber, and such deenergizationtakes place in response to a signal furnished by the speed counter meanswhen the speed of the rotary member reaches the predetermined value.

If the valve member is installed in a passage which conveys fuel fromthe high-pressure chamber to the low-pressure chamber, it is caused toopen in response to deenergization of the valve means, and suchdeenergization again takes place when the speed counter means produces asignal which is indicative of the predetermined maximum permissiblespeed of the rotary member.

The operative connection between the speed counter means and the windingof the valve means preferably includes an electrical or electronicregulating circuit having an amplifier whose input circuit contains aninductance of the speed changer means and a first safety fuse and whoseoutput circuit preferably contains a second safety fuse and a relaywhose switch is in circuit with the winding of the valve means.

The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved safety device itself, however, both as to its construction andits mode of operation, together with additional features and advantagesthereof, will be best understood upon perusal of the following detaileddescription of certain specific embodiments with reference to theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary partlydiagrammatic and partly sectional view of a diesel engine which embodiesone form of the improved safety device; and

FIG. 2 is a similar view of a diesel engine which embodies a modifiedsafety device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a portion ofa fuel injection pump which may be of the type disclosed in thecopending application, Ser. No. 12,409 filed Feb. 18, 1970 by Eheim etal. and assigned to the same assignee. The pump includes a pump piston13 which is reciprocable and rotatable in a pump housing 51 by therotary output shaft 50 of a diesel engine and serves to supply measuredquantities of fuel to several fuel lines 33 (only one shown). The fuelmetering unit which determines the beginning and the end of the intervalof fuel injection into each fuel line 33 comprises a collar 10 which ismovable axially of the piston 13, a rotary electromagnet 11, and anelectronic control circuit 12a which supplies to the electromagnet 11signals by way of an electrical connection 12, such signals serving todetermine the extent of energization of the electromagnet 11 and hencethe axial position of the collar 10. The manner in which the pump piston13 is rotated and moved axially in response to rotation of the rotarymember 50 is fully disclosed in the aforementioned application of Eheimet al. The housing 51 of the fuel injection pump defines a high-pressurefuel chamber 14 which is connected with a low-pressure fuel chamber 114by a fuel supplying passage 24 controlled by the pump piston 13 and by anovel electromagnetic safety valve 20. The shaft 50 carries a toothedgear-shaped element 34 of ferromagnetic material which cooperates with ayoke 15 having two serrated or toothed arms or extensions which areadjacent to the teeth of the element 34. The yoke 15 carries twoinductance coils 16 and 17. The coil 16 serves to transmit to thecontrol circuit 12a signals (by way of the connection 18) which areindicative of rotational speed of the shaft 50. Such signals influencethe energization of the electromagnet 11. The coil 17 supplies similarsignals to an electronic regulating circuit 19 which controls the safetyvalve 20. The parts 34, 15 and 17 constitute a speed counter whicheffects closing of the safety valve 20 when the rotational speed of theshaft 50 reaches a predetermined maximum permissible value.

The valve 20 comprises a ferromagnetic core 21 which is biased by aspring 22 and carries at one end a valve member 23. When the spring 22is free to expand, the valve member 23 engages a seat 24a in thefuel-supplying passage 24 to prevent the flow of fuel from the lowerpressure chamber 114 to the higher pressure chamber 14. The interior ofthe safety valve 20 is connected with the low-pressure chamber 114 bybores 25 which compensate for differences in pressure and insure thatthe core 21 can move axially in response to energization ordeenergization of the winding 20a.

The regulating circuit 19 includes an electronic amplifier 26 whoseinput is connected with the inductance 17 on the yoke 15. A first safetyfuse 27 is installed in the input circuit of the amplifier 26 and asecond safety fuse 29 is installed in its output circuit which furtherincludes a relay 28 having a relay switch 30 in the circuit of thewinding 20a. The latter circuit further includes a separate energysource 31. The relay switch 30 is connected in parallel with a normallyopen auxiliary switch 32; the switch 32 closes for a short interval oftime in response to actuation of the starter 52. Each fuel line 33delivers pressurized fuel to a separate fuel injection nozzle (notshown).

The operation:

When the engine is idle, i.e., when the shaft 50 is at a standstill, theamplifier 26 does not receive signals from the inductance l7 and therelay 28 is deenergized. Thus, the relay switch 30 is open and thewinding 20a of the safety valve 20 is deenergized so that the spring 22maintains the valve member 23 in engagement with the seat 24a andprevents entry of fuel into the high-pressure chamber 14. If the driverwishes to start the engine, the starter 52 is actuated and closes theauxiliary switch 32 to complete the circuit of the winding 20a whichmoves the core 21 against the opposition of the spring 22 so that thechamber 14 communicates with the chamber 114 by way of the passage 24.The auxiliary switch 32 opens automatically when the starter 52 isinactive but the engine is on and its shaft 50 rotates the element 34 ofthe speed counter to induce in the inductance 17 a voltage which causesthe amplifier 26 to energize the relay 28 and to thus close the switch30. The circuit of the winding 20a is completed and the valve member 23is held in open position even though the auxiliary switch 32 is open.The shaft 50 effects axial and angular movements of the pump piston 13which delivers to fuel lines 33 metered quantities of fuel from thehigh-pressure chamber 14. The quantities of such fuel are determined bythe collar whose axial position is a function of rotational speed of theshaft 50 (see the inductance coil 16) and also a function of certainother factors which influence the output signal from the control circuit12a to the electromagnet 11. Such additional factors include theposition of the gas pedal, the atmospheric pressure, and/or others.

The amplifier 26 is designed in such a way that it offers an accuratelydetermined constant input resistance which remains unchanged duringprolonged operation of the diesel engine. The strength of the currentflowing in the input circuit of the amplifier 26 is proportional tovoltage in the inductance l7, i.e., to rotational speed of the shaft 50.When the speed of the shaft 50 exceeds a permissible maximum value, thesafety fuse 27 responds and opens the input circuit to deenergize therelay 28 in the output circuit of the amplifier 26. The relay switch 30opens and the winding a is deenergized to permit closing of the valvemember 23 under the action of the spring 22 so that the flow of fuelfrom the chamber 114 to the chamber 14 is interrupted in response to anincrease in rotational speed of the shaft 50 beyond the permissiblevalue.

The second safety fuse 29 constitutes an optional feature of theregulating circuit 19. This fuse is provided to effect deenergization ofthe relay 28 and opening of the switch 30 in the event of failure of oneor more electronic or other components of the amplifier 26. For example,if a transistor in the amplifier 26 is damaged or destroyed, the outputcircuit of this amplifier might continue to furnish a high voltagesignal subsequent to opening of the input circuit by the safety fuse 27.The fuse 29 is designed to open the output circuit and to deenergize therelay 28 in response to the flow of a current which is indicative of themaximum permissible rotational speed of the shaft 50. Thus, the winding200 can be deenergized by the fuse 27 or by the fuse 29.

lt will be noted that the regulating circuit 19 serves the sole purposeof establishing an operative connection between the speed counter 15,17, 34 and the safety valve 20. The inductance 17 constitutes a discretegalvanically separated output element of the speed counter; this insuresthat the functioning of the improved safety device is independent ofadverse influences on the control circuit 12a or other parts of theengine.

FIG. 2 illustrates a portion of a second fuel injection pump wherein thesafety valve 20 is installed in a fuel returning passage 42 which candeliver fuel from the high-pressure chamber 14 to the low-pressurechamber 114. The body 40 of the safety valve 20 is immediately adjacentto the chamber 14 and is provided with ducts 41 which can establish aconnection for the flow of fuel from the chamber 14 to the passage 42when the winding 20a is deenergized in response to opening of the switch30. The valve member 23 of the core 21' is of conical shape and itsconical surface is biased away from a seat in the valve body 40 by thespring 22' as soon as the circuit of the winding 20a opens, i.e.,whenever the switch 30 is opened while the auxiliary switch 32 is open.

When the engine is idle, the switches 30, 32 are open, the winding 20ais deenergized and the spring 22 maintains the valve member 23 in openposition. Thus, the passage 42 between the chambers 114, 14 is open andfuel cannot be forced into the fuel lines 33. When the winding 20a isenergized in response to closing of the switch .30 or 32 in a manner asdescribed in connection with FIG. 1, the core 21 is moved axiallyagainst the opposition of the spring 22' and the valve member 23 movesto closed or sealing position to prevent the flow of fuel from thechamber 14 to the chamber 114. Thus, the pressure in chamber 14 can bebuilt up sufficiently to equal that pressure which is necessary toeffect admission of fuel into the cylinders of the engine. The risingpressure in the chamber 14 acts on the valve member 23 and assists thewinding 20a in maintaining the safety valve 20 in sealing position.

When the circuit of the winding 20a is opened on deenergization of therealy 28, the spring 22' is free to return the valve member 23' to openposition so that the pressure in the chamber 14 drops below that whichis necessary for admission of fuel into the cylinders. The valve member23' can move to scaling position (under the action of spring 22') notlater than in response to the first suction stroke of piston 13following the opening of switch 30. During such suction stroke of thepiston 13, the pressure in the chamber 14 drops sufficiently to permitopening of the valve member 23' under the bias of the spring 22'.

At least one of the safety fuses 27, 29 may be an electronic fuse whichis responsive to a predetermined voltage or intensity of current andwhich opens when the current intensity or voltage in the corresponding(input or output) circuit of the amplifier 26 exceeds a predeterminedvalue corresponding to the maximum permissible rotational speed of theshaft 50. Also, at least one of these fuses can be designed to completethe circuit as soon as the voltage or current strength drops below thatwhich is indicative of excessive rotational speed of the shaft 50.1n itssimplest form, the fuse 27 and/or 29 may include a fusible conductorwhich melts when the strength of the current in the correspondingcircuit rises beyond a permissible value.

It was found that the improved safety device (including the speedcounter 15, 17, 34, the regulating circuit 19 and the safety valve 20 or20') is at least as reliable as conventional centrifugal governors whichare used in many presently known diesel engines. It was also found thatthe expenditures involved in the provision and mounting of such safetydevice in an engine whose operation is regulated by an electroniccontrol circuit are warranted and reasonable, partly because theamplifier 26 can receive current from the source which supplies currentto the control circuit 12a and also because at least some components(such as the inductance 17) can be mounted on parts (yoke 15) which arenecessary for proper operation of the control circuit. The overall costof the components of the safety device is considerably less than that ofa conventional centrifugal governor. Furthermore, the improved safetydevice is so versatile that it can be used in nearly all types ofelectronically controlled diesel engines. The amplifier 26 and the fuses27, 29 can be readily designed to respond to a predetermined maximumspeed of the engine. Still another advantage of the improved safetydevice is that the fuel injection pump can deliver fuel to the fuellines 33 only at a time when the energy source 31 is in circuit with thewinding 20a or 200 of the safety valve 20 or 20. Thus, eventual damageto or malfunction of that part of the regulating circuit 19 whichincludes the amplifier 26 merely results in closing of the safety valve(FIG. 1) or opening of such valve (FIG. 2) to prevent delivery offuel tothe fuel lines 33.

Each circuit of the amplifier 26 can include two or more fuses.

A circuit, which works as a electronic fuse, is disclosed in thePublication from Siemens, Schaltungen mit Halbleiterbauelementen, Band2, 1965, page 163. An amplifier, capable of being used in the circuit 19FIG. 1 or FIG. 2 is disclosed in the same publication on page 117.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featureswhich fairly constitute essential characteristics of the generic andspecific aspects of my contribution to the art and, therefore, suchadaptations should and are intended to be comprehended within themeaning and range of equivalence of the claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

1. In an internal combustion engine, a combination comprising a fuelinjection pump having a high-pressure fuel chamber, a low-pressure fuelchamber, and a passage connecting said chambers; a rotary memberarranged to rotate at a variable speed which is proportional to theoperating speed of the engine; electromagnet safety valve meansincluding a valve member installed in said pump and movable between openand closed positions in which it respectively permits and prevents theflow of fuel through said passage, said valve member being arranged toassume one of said positions in response to energization and the otherof said positions in response to deenergization of said valve means;electrical speed counter means comprising a serrated ferromagneticelement driven by said rotary member, a yoke having at least oneserrated portion adjacent to said ferromagnetic element, a

first and a second inductance on said yoke; a regulating circuitconnecting said first inductance to said safety valve means to effect achange in the condition of energization of said safety valve means whenthe speed of said rotary member reaches a predetermined value; anelectric control circuit connected to said second inductance; and meansconnected to said electronic control circuit for regulating supply offuel by said injection pump to said engine in dependence on the speed ofsaid rotary member.

2. A combination as defined in claim 1, wherein said passage is arrangedto supply fuel from said low-pressure chamber to said high-pressurechamber and wherein said valve member is moved to closed position inresponse to said change in the condition of energization of said safetyvalve.

3. A combination as defined in claim 1, wherein said passage is arrangedto convey fuel from said high-pressure chamber to said lowpressurechamber and wherein said valve member is moved to open position inresponse to said change in the condition of energization of said safetyvalve.

4. A combination as defined in claim 1, wherein said regulating circuitconnecting said speed counter means with said valve comprises amplifiermeans having an input circuit including a portion of said speed countermeans and an output circuit arranged to effect changes in energizationof said safety valve means in dependency on the condition of said inputcircuit.

5. A combination as defined in claim 4, wherein said output circuitincludes a relay having a switch in circuit with said safety valvemeans.

6. A combination as defined in claim 5, wherein at least one of saidinput and output circuits includes a safety fuse arranged to open therespective circuit when the speed of said rotary member reaches saidpredetermined valve.

7. A combination as defined in claim 6, wherein said fuse is anelectronic fuse.

8. A combination as defined in claim 6, wherein each ofsaid input andoutput circuits includes at least one fuse.

9. A combination as defined in claim 1, further comprising starter meansactuatable to start the engine and means for effecting a change in thecondition of energization of said valve means in response to actuationof said starter means.

1. In an internal combustion engine, a combination comprising a fuelinjection pump having a high-pressure fuel chamber, a lowpressure fuelchamber, and a passage connecting said chambers; a rotary memberarranged to rotate at a variable speed which is proportional to theoperating speed of the engine; electromagnet safety valve meansincluding a valve member installed in said pump and movable between openand closed positions in which it respectively permits and prevents theflow of fuel through said passage, said valve member being arranged toassume one of said positions in response to energization and the otherof said positions in response to deenergization of said valve means;electrical speed counter means comprising a serrated ferromagneticelement driven by said rotary member, a yoke having at least oneserrated portion adjacent to said ferromagnetic element, a first and asecond inductance on said yoke; a regulating circuit connecting saidfirst inductance to said safety valve means to effect a change in thecondition of energization of said safety valve means when the speed ofsaid rotary member reaches a predetermined value; an electric controlcircuit connected to said second inductance; and means connected to saidelectronic control circuit for regulating supply of fuel by saidinjection pump to said engine in dependence on the speed of said rotarymember.
 2. A combination as defined in claim 1, wherein said passage isarranged to supply fuel from said low-pressure chamber to saidhigh-pressure chamber and wherein said valve member is moved to closedposition in response to said change in the condition of energization ofsaid safety valve.
 3. A combination as defined in claim 1, wherein saidpassage is arranged to convey fuel from said high-pressure chamber tosaid low-pressure chamber and wherein said valve member is moved to openposition in response to said change in the condition of energization ofsaid safety valve.
 4. A combination as defined in claim 1, wherein saidregulating circuit connecting said speed counter means with said valvecomprises amplifier means having an input circuit including a portion ofsaid speed counter means and an output circuit arranged to effectchanges in energization of said safety valve means in dependency on thecondition of said input circuit.
 5. A combination as defined in claim 4,wherein said output circuit includes a relay having a switch in circuitwith said safety valve means.
 6. A combination as defined in claim 5,wherein at least one of said input and output circuits includes a safetyfuse arranged to open the respective circuit when the speed of saidrotary member reaches said predetermined valve.
 7. A combination asdefined in claim 6, wherein said fuse is an electronic fuse.
 8. Acombination as defined in claim 6, wherein each of said input and outputcircuits includes at least one fuse.
 9. A combination as defined inclaim 1, further comprising starter means actuatable to start the engineand means for effecting a change in the condition of energization ofsaid valve means in response to actuation of said starter means.